How can I add more animation to my existing animation?
In order for the changes you make to an object to be saved, you need to insert a keyframe on the property or whatever it is that you changed. To do this, in this case, mouse over the color field and press I. 

Alternatively, you can open the graph editor, by selecting it from the dropdown that appears when you press thebutton on the bottom left corner of thewindow (in the default screen layout), and then edit the f-curves for the property you wish to change manually.